The present invention relates to the field of optics and particularly to the field of processing optical energy.
Sub-wavelength metal particles exhibit strong optical resonance due to the excitation of a localized plasma resonance in the particle. These resonances are associated with enhanced electromagnetic fields inside and adjacent the particle. These enhanced fields can be used to enhance optical processes in materials and molecules that are placed adjacent these particles. Examples of such optical processes include Raman scattering and second-harmonic generation as well as other optical processes whose strength depends on the size of the electric field at the species being excited or probed. These local field enhanced effects are well known in the art.
Although sub-wavelength sized particles have been found to have strong optical resonance properties, the local field enhanced effects have been under utilized because the enhanced field generated with sub-wavelength sized particles cannot be practically utilized.
What has unexpectedly been found is that sub-wavelength sized voids in a metal will exhibit localized plasma resonances and that sub-wavelength sized voids in a metal can be used to enhance emission and absorption of optical energy. Furthermore, it has been found that by employing the voids in an ordered array a cooperative effect between the voids can be obtained. The properties of sub-wavelength voids and the order arrays thereof can be used to enhance various optical processes and to create novel lasing devices and LED devices.
As such, the present invention is directed to an optical structure and method for processing optical energy comprising a metal layer having an upper surface and a lower surface, one or more of said surfaces having a plurality of voids, said voids preferably having a dimension less then the wavelength of optical energy being processed. The optical structure can be used to form a variety of devices including, but not limited to, a laser, an LED, a wavelength converter, a sensor and/or a switch.